This invention relates to dental posts, and more particularly to a method and apparatus utilizing a dental post system for the formation and retention of a dental restoration.
Various dental procedures are known which utilize dental posts in the restoration and reinforcement of devitalized dentition. In these procedures, dental posts are initially inserted into a prepared tooth stub. A dental restoration is then built up on the tooth stub. Prior to the building of the restoration, a core is first provided directly on the tooth stub, and it is upon the core that the restoration is fabricated.
In the various methods available, the tooth is first prepared to receive the dental post. The apical section of the canal is sealed with gutta percha. A bore is drilled into the tooth, typically along the canal, to a desired depth. In one known method, referred to as the stainless steel technique, a steel dental post is permanently cemented into the bore with a portion projecting from the tooth stub. A core is built up on the tooth stub encompassing the projecting end of the dental post. The core is formed of amalgom or composite material. The final restoration is then built up around the core.
Although this technique is useful for an economical and quick procedure, the core that is formed is only of amalgom or composite material and cannot provide the superiority of a metallic core, such as a gold core. The reason that the amalgom or composite core is utilized is that this material will adhere to the tooth stub and the projecting end of the dental post, and this core can be easily formed directly in the patient's mouth. Metallic material, on the other hand, would have to be cast and therefore cannot be formed directly in the patient's mouth, and furthermore if cast separately, the metallic material would not adhere directly onto the dental post and tooth stub, where additional cement or adhesive would be required.
In order to provide a metallic core, it is known to use either the direct or indirect technique. In the direct technique, an initial burn-out post is temporarily inserted into the bore formed into the tooth stub with a portion of the post projecting from the stub. Resin is then applied and shaped into a core. The resin together with the temporarily inserted post are then entirely removed from the tooth stub and used as a pattern which is sprued and invested using standard investment casting techniques in order to form a unitary metallic core and metallic post assembly in one piece. Typically, precious or non-precious alloys are utilized in the formation of the metal core and post. The core and post are cast together as a one piece unit, where this one piece core and post unit is reinserted into the channel in the tooth stub and permanently secured in place to form a foundation for the restorative dentistry.
In the indirect technique, again a temporary post is inserted into the tooth stub bore, and an impression is taken of the top of the tooth stub including the projecting portion of the dental post. A master model is then fabricated to form a positive. A suitable negative die is formed from this positive. The unitary core and post pattern is then fabricated using a conventional lost wax method or using self curing resin. From this pattern, through investment casting, a suitable one piece metallic core and post unit is cast. This unit can then be inserted into the tooth stub and permanently secured in place to form a foundation for the restorative dentistry.
In both the direct and indirect method, a temporary crown is usually formed during the time when the unitary metallic post and core unit is being cast. Once the metallic post and crown unit has been formed and inserted into the tooth stub, the suitable restoration can then be fabricated on the metallic core.
While both the direct and indirect methods are extremely useful and provide extremely strong restorations, they require the post and core to be formed as a one piece unit. Thus, the post must be made from the same material as the core, which in most cases is a precious metal, such as gold. Obviously, a stainless steel post would be stronger than a gold post, and a gold core is better than a stainless steel core, however the use of two different metals is not possible with the direct and indirect methods.
Accordingly, it would be superior to provide the best aspects of the various existing techniques. For example, it would be most effective to utilize the aspect of the stainless steel technique which permits the inserted metallic dental post to be permanently placed in the tooth stub bore. It would also be beneficial to provide for a precious metallic core which can be cast without the post, and then permanently secured onto the post. However, thus far, the prior art has not been able to provide for the most beneficial aspects of the existing techniques. In the prior art, the core and post were cast as a unitary structure since there was no suitable method or structure to permanently secure the cast core onto a metallic dental post.